//add this event listener somewhere
//"starstage" is the starling stage
//"flashstage" is the flash stage

starstage.addEventListener(ResizeEvent.RESIZE, onresize);

private static function onresize(e:ResizeEvent) {
    updategraphicsmode(e.width, e.height);
}

private static function updategraphicsmode(windowwidth:Int, windowheight:Int) {
        if (!_fullscreen) {
            if (flashstage.displayState == StageDisplayState.FULL_SCREEN_INTERACTIVE ||
                flashstage.displayState==StageDisplayState.FULL_SCREEN){
                flashstage.displayState=StageDisplayState.NORMAL;
            }
        }else {
            if (flashstage.displayState == StageDisplayState.NORMAL) {
              try {
                    flashstage.displayState = StageDisplayState.FULL_SCREEN_INTERACTIVE;
                }catch (e:Dynamic) {
                    #if flash
                    if (e.name == "SecurityError") {
                        if (flashstage.loaderInfo.url.indexOf("file://") == 0) {
                        }else {
                            Debug.log("Error: Haxegon is unable to toggle fullscreen in browsers due to Adobe security settings. To do: make haxegon_flash addon!");
                        }
                    }
                    #end
                }
            }
        }

        if (windowwidth == 0 && windowheight == 0) {
            //if returning to windowed mode from fullscreen, don't mess with the
            //viewport now; leave it to the onresize event to catch
            return;
        }

        starstage.stageWidth = screenwidth;
    starstage.stageHeight = screenheight;

        // set rectangle dimensions for viewPort:
        var stretchscalex:Float;
        var stretchscaley:Float;
        var stretchscalex:Float = Std.int(windowwidth) / screenwidth;
        var stretchscaley:Float = Std.int(windowheight) / screenheight;
        var stretchscale:Float = Math.min(stretchscalex, stretchscaley);

        var viewPortRectangle:Rectangle = new Rectangle();
        viewPortRectangle.width = screenwidth * stretchscale;
        viewPortRectangle.height = screenheight * stretchscale;

        viewPortRectangle.x = Std.int((windowwidth - Std.int(screenwidth * stretchscale)) / 2);
        viewPortRectangle.y = Std.int((windowheight - Std.int(screenheight * stretchscale)) / 2);
        // resize the viewport:
        Starling.current.viewPort = viewPortRectangle;
    }